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Abstract
Multiple neuroactive substances are secreted by neurons and/or glial cells and modulate the sensitivity to cell death. In the developing retina, it has been shown that increased intracellular levels of cAMP protect cells from degeneration. We tested the hypothesis that the neuroactive peptide pituitary adenylyl cyclase-activating polypeptide (PACAP) has neuroprotective effects upon the developing rat retina. PACAP38 prevented anisomycin-induced cell death in the neuroblastic layer (NBL) of retinal explants, and complete inhibition of induced cell death was obtained with 1 nm. A similar protective effect was observed with PACAP27 and with the specific PAC1 receptor agonist maxadilan but not with glucagon. Photoreceptor cell death induced by thapsigargin was also prevented by PACAP38. The neuroprotective effect of PACAP38 upon the NBL could be reverted by the competitive PACAP receptor antagonist PACAP6-38 and by the specific PAC1 receptor antagonist Maxd.4. Molecular and immunohistochemical analysis demonstrated PAC1 receptors, and treatment with PACAP38 induced phospho-cAMP-response element-binding protein immunoreactivity in the anisomycin-sensitive undifferentiated postmitotic cells within the NBL. PACAP38 produced an increase in cAMP but not inositol triphosphate, and treatment with the cAMP-dependent protein kinase inhibitor R(p)-cAMPS blocked the protective effect of PACAP38. The results indicate that activation of PAC1 receptors by PACAP38 modulates cell death in the developing retina through the intracellular cAMP/cAMP-dependent protein kinase pathway.
Highlights
Developmental cell death is a major event in neurogenesis, controlled by various secreted molecules, many of which play distinct roles in the mature nervous system
Protection against anisomycin-induced cell death was observed with PACAP27
PAC1 Receptors Expressed in the Neuroblastic Layer Are Functionally Active—We examined whether cells from the neuroblastic layer (NBL) responded to PACAP38 by testing for the induction of CREB phosphorylation
Summary
Developmental cell death is a major event in neurogenesis, controlled by various secreted molecules, many of which play distinct roles in the mature nervous system. Molecular and immunohistochemical analysis demonstrated PAC1 receptors, and treatment with PACAP38 induced phospho-cAMP-response elementbinding protein immunoreactivity in the anisomycinsensitive undifferentiated postmitotic cells within the NBL. The results indicate that activation of PAC1 receptors by PACAP38 modulates cell death in the developing retina through the intracellular cAMP/cAMP-dependent protein kinase pathway.
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